1 /*
2 * Copyright Andrey Semashev 2007 - 2015.
3 * Distributed under the Boost Software License, Version 1.0.
4 * (See accompanying file LICENSE_1_0.txt or copy at
5 * http://www.boost.org/LICENSE_1_0.txt)
6 */
7 /*!
8 * \file add_value.hpp
9 * \author Andrey Semashev
10 * \date 26.11.2012
11 *
12 * This header contains the \c add_value manipulator.
13 */
14
15 #ifndef BOOST_LOG_UTILITY_MANIPULATORS_ADD_VALUE_HPP_INCLUDED_
16 #define BOOST_LOG_UTILITY_MANIPULATORS_ADD_VALUE_HPP_INCLUDED_
17
18 #include <boost/type_traits/is_scalar.hpp>
19 #include <boost/type_traits/remove_cv.hpp>
20 #include <boost/type_traits/remove_reference.hpp>
21 #include <boost/type_traits/conditional.hpp>
22 #include <boost/log/detail/config.hpp>
23 #include <boost/log/detail/embedded_string_type.hpp>
24 #include <boost/log/attributes/attribute_name.hpp>
25 #include <boost/log/attributes/attribute_value_impl.hpp>
26 #include <boost/log/expressions/keyword_fwd.hpp>
27 #include <boost/log/sources/record_ostream.hpp>
28 #include <boost/log/detail/header.hpp>
29
30 #ifdef BOOST_HAS_PRAGMA_ONCE
31 #pragma once
32 #endif
33
34 #ifdef _MSC_VER
35 #pragma warning(push)
36 // 'boost::log::v2s_mt_nt6::add_value_manip<RefT>::m_value' : reference member is initialized to a temporary that doesn't persist after the constructor exits
37 // This is intentional since the manipulator can be used with a temporary, which will be used before the streaming expression ends and it is destroyed.
38 #pragma warning(disable: 4413)
39 // returning address of local variable or temporary
40 // This warning refers to add_value_manip<RefT>::get_value() when RefT is an rvalue reference. We store the reference in the manipulator and we intend to return it as is.
41 #pragma warning(disable: 4172)
42 #endif
43
44 namespace boost {
45
46 BOOST_LOG_OPEN_NAMESPACE
47
48 //! Attribute value manipulator
49 template< typename RefT >
50 class add_value_manip
51 {
52 public:
53 //! Stored reference type
54 typedef RefT reference_type;
55 //! Attribute value type
56 typedef typename remove_cv< typename remove_reference< reference_type >::type >::type value_type;
57
58 private:
59 // The stored reference type is an lvalue reference since apparently different compilers (GCC and MSVC) have different quirks when rvalue references are stored as members.
60 // Additionally, MSVC (at least 11.0) has a bug which causes a dangling reference to be stored in the manipulator, if a scalar rvalue is passed to the add_value generator.
61 // To work around this problem we save the value inside the manipulator in this case.
62 typedef typename remove_reference< reference_type >::type& lvalue_reference_type;
63
64 typedef typename conditional<
65 is_scalar< value_type >::value,
66 value_type,
67 lvalue_reference_type
68 >::type stored_type;
69
70 typedef typename conditional<
71 is_scalar< value_type >::value,
72 value_type,
73 reference_type
74 >::type get_value_result_type;
75
76 private:
77 //! Attribute value
78 stored_type m_value;
79 //! Attribute name
80 attribute_name m_name;
81
82 public:
83 //! Initializing constructor
add_value_manip(attribute_name const & name,reference_type value)84 add_value_manip(attribute_name const& name, reference_type value) : m_value(static_cast< lvalue_reference_type >(value)), m_name(name)
85 {
86 }
87
88 //! Returns attribute name
get_name() const89 attribute_name get_name() const { return m_name; }
90 //! Returns attribute value
get_value() const91 get_value_result_type get_value() const { return static_cast< get_value_result_type >(m_value); }
92 };
93
94 //! The operator attaches an attribute value to the log record
95 template< typename CharT, typename RefT >
operator <<(basic_record_ostream<CharT> & strm,add_value_manip<RefT> const & manip)96 inline basic_record_ostream< CharT >& operator<< (basic_record_ostream< CharT >& strm, add_value_manip< RefT > const& manip)
97 {
98 typedef typename aux::make_embedded_string_type< typename add_value_manip< RefT >::value_type >::type value_type;
99 attribute_value value(new attributes::attribute_value_impl< value_type >(manip.get_value()));
100 strm.get_record().attribute_values().insert(manip.get_name(), value);
101 return strm;
102 }
103
104 //! The function creates a manipulator that attaches an attribute value to a log record
105 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
106
107 template< typename T >
add_value(attribute_name const & name,T && value)108 inline add_value_manip< T&& > add_value(attribute_name const& name, T&& value)
109 {
110 return add_value_manip< T&& >(name, static_cast< T&& >(value));
111 }
112
113 //! \overload
114 template< typename DescriptorT, template< typename > class ActorT >
115 inline add_value_manip< typename DescriptorT::value_type&& >
add_value(expressions::attribute_keyword<DescriptorT,ActorT> const &,typename DescriptorT::value_type && value)116 add_value(expressions::attribute_keyword< DescriptorT, ActorT > const&, typename DescriptorT::value_type&& value)
117 {
118 typedef typename DescriptorT::value_type value_type;
119 return add_value_manip< value_type&& >(DescriptorT::get_name(), static_cast< value_type&& >(value));
120 }
121
122 //! \overload
123 template< typename DescriptorT, template< typename > class ActorT >
124 inline add_value_manip< typename DescriptorT::value_type& >
add_value(expressions::attribute_keyword<DescriptorT,ActorT> const &,typename DescriptorT::value_type & value)125 add_value(expressions::attribute_keyword< DescriptorT, ActorT > const&, typename DescriptorT::value_type& value)
126 {
127 return add_value_manip< typename DescriptorT::value_type& >(DescriptorT::get_name(), value);
128 }
129
130 //! \overload
131 template< typename DescriptorT, template< typename > class ActorT >
132 inline add_value_manip< typename DescriptorT::value_type const& >
add_value(expressions::attribute_keyword<DescriptorT,ActorT> const &,typename DescriptorT::value_type const & value)133 add_value(expressions::attribute_keyword< DescriptorT, ActorT > const&, typename DescriptorT::value_type const& value)
134 {
135 return add_value_manip< typename DescriptorT::value_type const& >(DescriptorT::get_name(), value);
136 }
137
138 #else // !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
139
140 template< typename T >
add_value(attribute_name const & name,T const & value)141 inline add_value_manip< T const& > add_value(attribute_name const& name, T const& value)
142 {
143 return add_value_manip< T const& >(name, value);
144 }
145
146 template< typename DescriptorT, template< typename > class ActorT >
147 inline add_value_manip< typename DescriptorT::value_type const& >
add_value(expressions::attribute_keyword<DescriptorT,ActorT> const &,typename DescriptorT::value_type const & value)148 add_value(expressions::attribute_keyword< DescriptorT, ActorT > const&, typename DescriptorT::value_type const& value)
149 {
150 return add_value_manip< typename DescriptorT::value_type const& >(DescriptorT::get_name(), value);
151 }
152
153 #endif // !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
154
155 BOOST_LOG_CLOSE_NAMESPACE // namespace log
156
157 } // namespace boost
158
159 #ifdef _MSC_VER
160 #pragma warning(pop)
161 #endif
162
163 #include <boost/log/detail/footer.hpp>
164
165 #endif // BOOST_LOG_UTILITY_MANIPULATORS_ADD_VALUE_HPP_INCLUDED_
166